In medical procedures a minimally invasive device that can be localized with a high spatial accuracy in real time in 3D and that is able to measure the number of photons reaching the tip of the device may be valuable. E.g., in 4D radiation therapy such a device may be located in the close vicinity of a tumor or even be inserted into the tumor. During radiation therapy the device may then measure the applied dose which is hitting the tumor accurately inside the body of the patient. At the same time the device may provide the 4D position of the tumor during radiation therapy. Thus, high precision radiation therapy can be applied to the tumor. There may well be other medical or non-medical procedures which may profit from such a device. In the following, a very efficient and compact device is introduced and discussed.
As stated above, the present invention generally concerns tracking of elongated devices, particularly optical tracking of medical devices (e.g., endoscopes, catheters and guidewires). The flexible x-ray detector with optical shape sensing may be used for a three-dimensional (“3D”) shape reconstruction. The flexible x-ray detector with optical shape sensing utilizes an optical fiber embedded within an elongated device.
The art of shape reconstruction of a multi-core fiber generally involves three steps.
The first step involves a multi-core fiber being interrogated with optical frequency domain reflectometry, which results in the measurement of both an amplitude and a phase of a reflection for each core as a function of wavelength. The reflection may be invoked by embedded periodical structures (e.g., Fiber Bragg Gratings) or by non-periodic, random variations in the refractive index (e.g., Rayleigh scattering).
The second step involves a calculation of strain in each core at multiple positions along the fiber from the reflection spectra.
The third step involves a 3D shape reconstruction of the optical fiber by means of combining the various strain data. In particular, the strain measurements may be converted to rotation angles and the associated rotation matrices may be used to update a tangent vector, a normal vector and a binormal vector (i.e. columns of a Jacobian matrix). However, the art fails to address how the line elements of the fiber are calculated or how the matrix for converting the strain measurements is established.
The inventor of the present invention has appreciated that an improved device for combined detection of position and radiation dose is of benefit, and has in consequence devised the present invention.